(1) Field of the Invention
The present invention relates to an apparatus and method for processing fuel vapor in an internal combustion engine constituted to adsorb the fuel vapor generated in a fuel tank to a canister, and to supply a purged air of the canister to the intake air passage of the engine for combustion.
(2) Related Art of the Invention
A fuel vapor processing apparatus is conventionally known for absorbing the fuel vapor generated in the fuel tank to a canister temporarily, while introducing new air into the canister by the negative pressure of a throttle valve so as to purge the fuel vapor, and then supplying the purged air into the engine for combustion (refer for example to Japanese Unexamined Utility Model Publication No. H1-58760).
According to the structure as shown above where the purging is performed by the negative pressure of the throttle valve, there was a problem that the purged air may not be supplied when the pressure inside the intake air passage is changed to positive pressure due to a supercharge, in the case where the purge passage is communicated to the intake air passage on the downstream side of a compressor in a combustion engine equipped with a supercharger.
The purged air may be supplied during supercharged states by applying a structure to communicate the purge passage to the intake air passage on the upstream side of the compressor. However, due to the change in pressure on the upstream side of the compressor according to various driving conditions, there was a problem that the flow rate of the purged air may not be controlled accurately.